Psychologists at Cardiff University believe psychopaths' emotional detachment can be used to identify them.

Their adapted test flashes up a series of words on a screen, one after another.

This test may become an important tool for distinguishing psychopaths who are likely to commit extremely violent offences from those who are not

Cardiff University researchers

The individual has to classify each word as either "pleasant" or "unpleasant" and either "violent" or "peaceful".

They press one of two buttons - one for "pleasant" or "peaceful" actions and another for "unpleasant" or "violent" actions.

However, the task becomes much more difficult if the buttons represent conflicting emotions - if one button is for "pleasant" and "violent" and the other is for "peaceful" and "unpleasant".

For instance, if "blood" or "peace" flashes up, ordinary people will generally take longer to decide which buttons to press, taking time to consider each word carefully.

However, tests on psychopaths have shown that they do not need this extra time and choose the "right" answer no matter how the buttons are configured.

The researchers tested 121 male convicts. Of these, 13 were psychopathic murderers; 17 were non-psychopathic
murderers; 39 were psychopaths who had committed offences other than
murder; and the remaining 52 were non-psychopaths who had committed
offences other than murders.

Faster answers

They found that psychopaths answered much more quickly than any of the other men involved in the study. This difference remained significant even when they adjusted for IQ levels.

"With psychopathic murderers, there's almost no difference between whether we put the 'violent' words with 'pleasant' (ones), or the 'violent' words with 'unpleasant' ones. They are just as
fast," said psychologist Robert Snowden, one of those involved in the study.

Writing in the journal Nature, the researchers suggested that the fast responses of psychopaths may be linked to their "abnormal social beliefs" about
violence.

"Psychopathic murderers have diminished negative reactions to violence compared with non-psychopathic murders and other
offenders," they wrote.

The researchers suggested their test could be used to identify those psychopaths who are most likely to carry out violent acts.

"This test may become an important tool for distinguishing psychopaths who are likely to commit extremely violent offences from those who are not," they wrote.